• ETRI Journal
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• 제36권3호
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• pp.374-384
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• 2014

To achieve high-speed (giga-bit) connectivity for short-range wireless multimedia applications, the millimeter-wave (mmWave) wireless personal area networks with directional antennas are gaining increased interest. Due to the use of directional antennas and mmWave communications, the probability of non-interfering transmissions increases in a localized region. Network throughput can be increased immensely by the concurrent time allocation of non-interfering transmissions. The problem of finding optimum time allocation for concurrent transmissions is an NP-hard problem. In this paper, we propose two enhanced versions of previously proposed multi-hop concurrent transmission (MHCT) schemes. To increase network capacity, the proposed schemes efficiently make use of the free holes in the time-allocation map of the MHCT scheme; thus, making it more compact.

• 정보와 통신
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• 제34권6호
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• pp.3-10
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• 2017

최근 운전자의 편의성과 안전성 향상을 위한 커넥티드 카 및 자율주행 차량에 대한 관심과 연구가 집중되고 있다. 이러한 커넥티드 카와 자율주행 차량의 경우 대용량의 멀티미디어 전송 및 센서 데이터 공유 등 다양한 서비스를 위해 높은 전송용량과 신뢰성을 보장할 수 있는 vehicle-to-vehicle (V2V) 통신과 vehicle-to- infrastructure (V2I) 통신에 대한 기본적인 연구와 구현이 필수적이다. 이러한 요구사항을 만족시키기 위해서 최근 mmWave 기반의 V2V, V2I에 대한 연구가 큰 주목을 받고 있다. 본고에서는 mmWave 대역 V2V 및 V2I 기술의 필요성과 채널에 관련된 기존 연구를 살펴보고, 이를 기반으로 현재까지 연구된 mmWave 대역 V2V, V2I 관련 연구에 대해 살펴보고자 한다. 또한 기존 연구의 한계점을 확인하고, 향후 연구방향과 주제에 대해 논의하고자 한다.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2003년도 종합학술발표회 논문집 Vol.13 No.1
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• pp.487-491
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• 2003

Design procedure of corrugated horn antenna for mm-wave frequency range is presented, and hybrid condition in horn is calculated. Balanced hybrid mode should be converted in the horn from TE11 mode by the proper corrugation dimensions which size are available to be fabricated under the mm-wave short wavelength condition. In this paper, corrugate profiles which satisfy both hybrid condition and fabrication possibility are obtained.. By cylindrical mode theory, the electromagnetic fields both inside hem and corrugation are delivered. Propagation characteristics in hem is calculated by the mode impedance matching method with boundary conditions, and radiation fields are obtained by the Kirchhoff-Hyugen principle to the hem aperture fields. A mm-wave corrugated horn operates on 85 - 115GHz is designed and fabricated, and results of measurement are also shown.

• 한국환경과학회:학술대회논문집
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• 한국환경과학회 2003년도 International Symposium on Clean Environment
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• pp.37-42
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• 2003

We have analyzed the characteristics of the sea surface winds and wind waves near the Korean marginal seas on the basis of prediction results of the sea surface winds from MM5/KMA model, which is being used for the operation system at the Korea Meteorological observation buoy data to verify the model results during Typhoon events. The correlation coefficients between the models and observation data reach up to about 95％, supporting that these models satisfactorily simulate the sea surface winds and wave heights even at the coastal regions. Based on these verification results, we have carried out numerical experiments about the wave modulation. When there exist an opposite strong current for the propagation direction of the waves or wind direction, wave height and length gets higher and shorter, and vice versa. It is proved that these modulations of wave parameters are well generated when wind speed is relatively week.

• Restorative Dentistry and Endodontics
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• 제33권6호
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• pp.518-525
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• 2008

본 연구의 목적은 제 IV형 근관에서 Continuous Wave 가압법을 이용하여 충전할 때 System B Plugger tip의 깊이에 따른 근단부 밀폐효과를 평가하기 위함이다. 50개의 J형 만곡을 갖는 레진 블록에 부러진 F3 ProTaper 파일을 이용해 근관장에서 3mm 지점에 ledge를 형성한 후, F1 ProTaper Ni-Ti file을 이용해 레진 블록을 천공시켜 제 IV형 근관을 형성하고 System B Plugger tip의 깊이에 따라 3개의 실험군과 1개의 대조군으로 분류하였다. 제 IV형 근관의 거터퍼쳐와 실러의 길이는 확대경하에서 캘리퍼를 이용해 측정하였고 다음과 같은 결과를 얻었다. 1. 대조군의 설측 근관에서 거터퍼쳐와 실러 모두 관찰되지 않았다. 2. 3 mm군에서는 5 mm 또는 7 mm군에 비해 유의하게 많은 거터퍼쳐의 충전이 관찰되었다 (p<0.05). 3. 7 mm군에서는 유의하게 많은 빈 공간이 관찰되었다 (p<0.05).

• 한국항해항만학회지
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• 제30권9호
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• pp.763-766
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• 2006

In this paper, the EM wave absorbers were designed and fabricated for X -band sensors using Carbon of dielectric material with CPE. The complex relative permittivity of samples is calculated by using measurement results of S-parameter. We simulated the double-layered type EM wave absorber with broad bandwidth using the measured complex relative permittivity by changing the thickness and layer, which was fabricated based on the simulated design The fabricated EM wave absorber consists of 1 mm first layer sheet facing metal with Carbon composition ratio 70 vol. % and 1.5 mm second layer sheet with Carbon composition ratio 60 vol. %. The measured results showed a good agreement to the simulated ones. It is found toot the optimized absorption ability of double-layered type EM wave absorber with thickness of 2.5 mm is higher than 10 dB from 7.8 GHz to 13.3 GHz.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 International Symposium on GPS/GNSS Vol.1
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• pp.297-300
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• 2006

In this paper, the EM wave absorbers were designed and fabricated for X-band sensors using Carbon of dielectric material with CPE. The complex relative permittivity of samples is calculated by the measured S-parameter data. We simulated the double-layered type EM wave absorber with broad bandwidth using the measured complex relative permittivity by changing the thickness and layer, which was fabricated based on the simulated design. The fabricated EM wave absorber consist of 1mm first layer sheet facing metal with Carbon composition ratio 70 vol% and 1.5 mm second layer sheet with Carbon composition ratio 60 vol%. The comparisons of simulated and measured results are good agreement. As a result, the optimized absorption ability of double-layered type EM wave absorber with thickness of 2.5 mm is higher than 10 dB from 7.8 GHz to 13.3 GHz.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2000년도 봄 학술발표회논문집
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• pp.119-124
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• 2000

The radar method is becoming one of the major nondestructive testing (NDT) techniques for concrete structures. Numerical modeling of electromagnetic wave is needed to analyze radar measurement results and to study the influence of measurement parameters on the radar measurements. Finite difference-time domain (FD-TD) method is used to simulate electromagnetic wave propagation through concrete specimens. Three concrete specimens with a 25 mm delamination embedded at 25 mm, 50 mm, and 75mm depth are modeled in 3-dimension. Also, thickness change of delamination and permittivity change are modeled.

• Clinical Pain
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• 제15권2호
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• pp.92-96
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• 2016

Objective: High frequency wave has been used in cancer treatment and cosmetic area but not in musculoskeletal pain yet. The purpose of this study is to evaluate temperature distribution according to depth and confirm safety of high frequency wave through animal study. Method: High frequency wave was applied to the posterior limb of 9 Sprague-Dawley rats for 20 minutes (experimental group) and no wave was used in the same number of rats for control group. Tissue temperature was measured from skin surface to 1 cm depth (surface, 1 mm, 5 mm, and 1 cm) for 5 seconds. Results: In the experimental group, temperature was elevated 3.2℃ at skin surface, 2.87℃ at 1 mm, 2.25℃ in 5 mm, and 1.74℃ in 1 cm depth. These were significantly different from those in the control group (p<0.001). There was no bulla or redness in the skin after high frequency wave stimulation and neither change of myocytes nor collagen degeneration was found in the tissue histology. There was no apoptosis in the skin surface and muscle layer in TUNEL assay. Conclusion: High frequency wave elevated tissue temperature from the skin to muscle layer without both histologic change and apoptosis.

• 대한치과기공학회지
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• 제23권2호
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• pp.189-202
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• 2002

A study on reflective spectrum between In-Ceram alumina plate(IAP) and IPS empress 2 plate were carried out in order to determine the difference of reflective spectrum rates between materials and between thicknesses of materials(0.8mm, 1.0mm, 1.2mm) by visible wave. The rates are measured by spectrophotometer(Top scan model TC-1800). And an analysis of ANOVA and paired sample t-test were carried out. The results are summarized as follows. 1. The reflective rates of IAP and IPS increased slowly as visible wave spectrum increased. 2. The difference of reflective rates of IAP between 0.8mm and 1.0mm is significant but a little(less than 1%). The differences of reflective rates of IAP between 0.8mm and l.2mm and between 1.0mm and l.2mm are significant(8%, 10% ). 3. The differences of reflective rates of IPS between 0.8mm and 1.0mm and between 0.8mm and 1.2mm and between 1.0mm and 1.2mm are significant(0.06 %, 0.01 %, 2 %). 4. The differences of reflective rates of 0.8mm, 1.0mm between IAP and IPS are significant but a little(less than 0.9%, 0.5%). The difference of reflective rates of l.2mm between IAP and IPS is significant and larger than the other thicknesses relatively(7 %).